β2 Adrenergic receptor agonists are recognized as effective drugs for the treatment of pulmonary diseases such as asthma and chronic obstructive pulmonary disease (including chronic bronchitis and emphysema). β2 Adrenergic receptor agonists are also recognised as useful for treating premature labour, and are potentially useful for treating neurological disorders and cardiac disorders.
International Patent Application WO 01/42193 and corresponding U.S. Pat. No. 6,576,793 disclose inter alia a novel compound of the formula (I):
wherein the stereochemistry at *C and **C may be inter alia (R) and (R). This compound may be more particularly represented by the formula (Ia):

Compound (Ia) may variously be referred to by the chemical names N-{2-[4-((R)-2-hydroxy-2-phenylethylamino)phenyl]ethyl}-(R)-2-hydroxy-2-(3-formamido-4-hydroxyphenyl)ethylamine; N-[3-[(1R)-1-hydroxy-2-[[2-[4-[((2R)-2-hydroxy-2-phenylethyl)amino]phenyl]ethyl]amino]ethyl-6-hydroxyphenyl]-formamide and (α-R)-3-formamido-4-hydroxy-(α-[[[p-(N-((2R)-hydroxy-phenethyl))-amino-phenethyl]amino]methyl benzyl alcohol. In CAS format the compound (Ia) is designated:    N-[2-hydroxy-5-[(1R)-1-hydroxy-2-[[2-4-[[(2R)-2-hydroxy-2-phenylethyl]amino]phenyl]ethyl]amino]ethyl]phenyl]-formamide.
WO 01/42193 and U.S. Pat. No. 6,576,793 disclose Compound (Ia) as a potent 132 adrenergic receptor agonist.
WO 01/42193 and U.S. Pat. No. 6,576,793 describe the preparation of compound (Ia) as a mixture of stereoisomers, that is, wherein the stereochemistry at *C is (RS) and the stereochemistry at **C is (RS), according to the following reaction scheme:
wherein Bn represents a benzyl protecting group.
U.S. patent application Ser. No. 10/627,555 and corresponding International published application WO 04/011416 describe the crystalline dihydrochloride salt of compound (Ia) and methods for preparing said salt. In said applications, compound (Ia) is prepared according to the following reaction scheme 2:

In Scheme 2 the abbreviations used have the following meanings:
NaHMDS: sodium hexamethyldisilazane
THF: tetrahydrofuran
DMPU: 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)pyrimidinone
TBDMSCl: tert-butyldimethylsilylchloride
DMF: dimethylformamide
DMSO: dimethylsulphoxide
TREAT HF: triethylamine trihydrofluoride
The numbering of compounds in Scheme 2 follows that in WO 04/011416, but it will be appreciated that compound 1 in Scheme 2 is equivalent to compound (Ia) herein.
According to WO 04/011416, the dihydrochloride salt of compound 1 is prepared by dissolving compound 1 in a polar solvent to form a first solution and adding hydrochloric acid to form a second solution from which the dihydrochloride salt is formed by crystallisation.
WO 2004/106279 (claiming priority from U.S. Patent Application Ser. No. 60/473,423) describes a crystalline form of N-{2-[4-((R)-2-hydroxy-2-phenylethylamino)phenyl]ethyl}-(R)-2-hydroxy-2-(3-formamido-4-hydroxyphenyl)ethylamine monohydrochloride.
WO 2004/106279 describes inter alia the following methods for preparing the crystalline monohydrochloride salt of compound 1:
i) the addition of between about 0.9 and about 1 molar equivalent of aqueous hydrochloric acid to the active compound 1 dissolved in a polar solvent, such as isopropanol or water;
ii) the addition of a molar excess of an aqueous solution of an inorganic chloride at a pH of between about 5 and about 6 to the active compound 1 dissolved in a polar, water soluble solvent. A suitable source of chloride ions is ammonium chloride and a suitable polar solvent is isopropanol. For example the crystalline monoHCl salt can be formed by dissolving compound 1 in isopropanol, adding aqueous ammonium chloride, and allowing the solution to stand overnight at room temperature. The crystalline product can be isolated by filtration and dried.iii) from a water slurry of the corresponding dihydrochloride salt, which slurry may be formed by the addition of water is added to the diHCl salt of compound 1.iv) recrystallizing a hydrochloride salt of compound 1 having between 1 and 2 equivalents of chlorine per mole of compound 1.